The project will focus on the biochemical mechanisms which determine the combination of benzo(a)pyrene metabolites with cellular DNA and which lead to gene mutations. The metabolism of benzo(a)pyrene will be studied in liposomes reconstituted from purified P450 cytochromes, P450 reductase, oxide-hydrase and selected lipids, with rat liver microsomes or nuclear envelope after induction by various agents. The biophysical characteristics, particularly fluidity, of these membrane preparations will be investigated and related to Benzo(a)pyrene metabolism. The conjugation of benzo(a) pyrene metabolites with various DNA molecules will be examined in these systems. Analytical techniques will be established to identify and quantitate nucleoside-metabolite conjugates obtained by hydrolysis of metabolite-modified DNA. The production of benzo(a)pyrene metabolites and the formation of metabolite nucleoside conjugates will be examined in isolated nuclei and whole cells from rat liver and lung. The modification of DNA in these systems will be examined in terms of parental DNA, newly synthesized DNA, euchromatin, heterochromatin and the production of DNA breaks. These parameters will be examined to explain the sensitivity of lung cells but not hepatocytes to oncogenic transformation by benzo(a)pyrene.